XTP II CrossPoint Series • Ethernet Connection
97
Subnetting — A Primer
It is not the purpose of this guide to describe TCP/IP protocol in detail. However, some
understanding of TCP/IP subnetting (a subnet is a subset of a network — a set of IP devices
that have portions of their IP addresses in common) is necessary in order to understand
the interaction of the XTP II CrossPoint Series matrix switcher and the mail server gateway.
To understand subnetting at the level required to install and operate the XTP II CrossPoint
Series matrix switcher, you must understand the concepts of a gateway, analog and remote
devices, IP addresses and octets, and subnet masks and octets.
Gateways
The XTP II CrossPoint Series matrix switcher can communicate with the e-mail server that
the matrix switcher uses for e-mail notification directly (if they are on the same subnet) or
the communication can be routed via a gateway (a computer that provides a link between
different subnets).
Analog and Remote Devices
The analog and remote devices are defined from the point of view of the function being
described. In this guide, subnetting is an issue when you are using the controlling PC to set
TCP/IP and e-mail values in the matrix switcher (see
When you are setting up the variables for e-mail notification, which may include subnetting,
the matrix switcher is the analog device and the e-mail server is the remote device.
IP Addresses and Octets
Valid IP addresses consist of four 1-, 2-, or 3-digit numeric subfields, properly called
“octets,” separated by dots (periods) (see figure 54). Each octet can be numbered from 000
through 255. Leading zeroes, up to three digits total per octet, are optional. Values of 256
and above are invalid.
192.168.254.254
Typical IP Address:
Octets
Figure 54.
Typical IP Address
Subnet Masks and Octets
The subnet mask (see figure 55) is used to determine whether the analog and remote
devices are on the same subnet or different subnets. The subnet mask consists of four
numeric octets separated by dots. Each octet can be numbered from 000 through 255.
Leading zeroes, up to three digits total per octet, are optional. Each octet typically contains
either 255 or 0. The octets determine whether or not the same octets of two IP addresses
will be compared when determining if two devices are on the same subnet.
255.255.0.0
Typical Subnet Mask:
Octets
255 indicates that this octet will be
compared between two IP addresses.
0 indicates that this octet will
not
be
compared between two IP addresses.
Figure 55.
Typical Subnet Mask
